From 29c8f983293538eb485c055b53f574c959a97ea3 Mon Sep 17 00:00:00 2001
From: Guillaume Ballet <3272758+gballet@users.noreply.github.com>
Date: Thu, 10 Aug 2023 21:38:07 +0200
Subject: [PATCH] save last MPT root for transition

---
 core/state/database.go | 11 +++++++++++
 core/state/statedb.go  |  9 ++++++++-
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/core/state/database.go b/core/state/database.go
index c6ebbd1fba..7ee8489d3f 100644
--- a/core/state/database.go
+++ b/core/state/database.go
@@ -92,6 +92,8 @@ type Database interface {
 	SetCurrentPreimageOffset(int64)
 
 	AddRootTranslation(originalRoot, translatedRoot common.Hash)
+
+	SetLastMerkleRoot(root common.Hash)
 }
 
 // Trie is a Ethereum Merkle Patricia trie.
@@ -272,6 +274,7 @@ type cachingDB struct {
 	origRoots           [32]common.Hash
 	translationIndex    int
 	translatedRootsLock sync.RWMutex
+	LastMerkleRoot      common.Hash // root hash of the read-only base tree
 
 	addrToPoint *utils.PointCache
 
@@ -379,6 +382,10 @@ func (db *cachingDB) OpenStorageTrie(stateRoot common.Hash, address common.Addre
 		}
 	}
 	if db.started {
+		mpt, err := db.openStorageMPTrie(db.LastMerkleRoot, address, root, nil)
+		if err != nil {
+			return nil, err
+		}
 		// Return a "storage trie" that is an adapter between the storge MPT
 		// and the unique verkle tree.
 		switch self := self.(type) {
@@ -506,3 +513,7 @@ func (db *cachingDB) GetStorageProcessed() bool {
 func (db *cachingDB) AddRootTranslation(originalRoot, translatedRoot common.Hash) {
 	db.AddTranslation(originalRoot, translatedRoot)
 }
+
+func (db *cachingDB) SetLastMerkleRoot(root common.Hash) {
+	db.LastMerkleRoot = root
+}
diff --git a/core/state/statedb.go b/core/state/statedb.go
index a3d320e6f8..a3616e7a58 100644
--- a/core/state/statedb.go
+++ b/core/state/statedb.go
@@ -1051,7 +1051,14 @@ func (s *StateDB) IntermediateRoot(deleteEmptyObjects bool) common.Hash {
 	if metrics.EnabledExpensive {
 		defer func(start time.Time) { s.AccountHashes += time.Since(start) }(time.Now())
 	}
-	return s.trie.Hash()
+	root := s.trie.Hash()
+
+	// Save the root of the MPT so that it can be used during the transition
+	if !s.Database().InTransition() && !s.Database().Transitioned() {
+		s.Database().SetLastMerkleRoot(root)
+	}
+
+	return root
 }
 
 // SetTxContext sets the current transaction hash and index which are